全封闭Ar气保护电渣重熔GH4169合金

上海五钢采用ALD 5t全封闭Ar气保护电渣重熔炉 ESR(Ar)冶炼了GH4 16 9合金锭 ,分析结果表明 ,ESR(Ar)电渣锭氧、硫含量和锭头尾碳、铝、钛之差远低于一般ESR工艺 ;VIM(真空感应熔炼 ) +ESR(Ar)工艺冶炼合金中平均氧含量 6× 10 - 6 远低于VIM +VAR(真空电弧重熔 )工艺冶炼合金中平均氧含量 13× 10 - 6 ,所以ESR(Ar)工艺脱氧效果优于VAR工艺     

重熔与时效工艺对ZL101铝合金组织与抗拉强度的影响

ZL101铝合金重熔后,浇注时间和浇注位置对其组织与性能影响很大。从ZL101铝合金不同浇注时间、不同浇注的位置取样,对铸态和时效后的试样进行抗拉强度性能测试,用光学显微镜观察其微观组织,研究重熔与时效工艺对ZL101铝合金组织与性能的影响规律。结果表明,在浇注过程中,试样的晶粒先发生粗化,随着浇注时间的延长,晶粒又发生细化。其抗拉强度也是先降低而后又升高。随着浇注位置的变化,由下向上晶粒逐渐粗化,共晶硅的分布逐渐变得不均匀,且抗拉强度逐渐降低。合金的时效与铸态的组织、性能的变化规律一致。     

Feasibility of laser surface treatment of pearlitic and bainitic ductile irons for hot rolls

The effects of laser surface treatment on the microstructure, crackability and stresses generated on laser hardened layers produced in several ductile cast iron materials were investigated. Two kinds of alloys having pearlitic (SGP) and acicular (SGA) matrix microstructures were selected. Hardened layers with thicknesses ranging from 1.5 to 2.5 mm were obtained by means of laser remelting (LSRm) or laser hardening (LSH). Thermal stresses generated upon laser processing have been estimated by a simple thermal model. For energy densities delivered onto the material at above 40 J/mm², extensive cracking was developed in SGA and SGP irons due to the contribution of thermal stresses. By lowering the energy density, crack formation was avoided in SGP irons only. At low energy densities, crack formation is controlled by the generation of transformational stresses due to excessive austenite retention. An increase of the surface temperature or the alloying content gave rise to an increase of the retained austenite and the formation of lower bainite at the remelted zone and the heat affected zones, respectively. K_C fracture toughness of Fe₃C carbides embedded in pearlitic and acicular matrixes was measured by means of the nano-indentation technique. Fracture toughness of cementite in SGP irons was slightly higher than in SGA irons, which can help to reduce the crackability of LSH layers.     

Al2O3 loss prediction model of selective laser melting Al2O3–Al composite

The element/phase loss is undesirable but existing during selective laser melting (SLM) of materials with volatile element/phase, which not only changes the material composition but also affects the molten pool flow. In the previous researches, the effect of remelting on the element/phase loss was neglected during the SLM process, instead, laser energy density was thought to be uppermost. In fact, the SLM process fabricates the parts in a manner of line by line and layer by layer, i.e., additive character, and the remelting in the overlap zone occurs during the SLM process. In this paper, three different Al₂O₃ loss prediction models of SLM Al₂O₃–Al composite by considering the additive character of SLM and the distribution of the Al₂O₃ associated with the different molten pool driving forces were developed. By comparing with the experimental results and predicted results, it is found that the Al₂O₃ is distributed on both sides of the molten pool under the combined action of the Marangoni flow and the evaporation recoil pressure. This kind of Al₂O₃ distribution enhances the effect of the remelting on the Al₂O₃ loss, i.e., the remelting brings a logarithmic increase in the Al₂O₃ loss rate. This determines the final Al₂O₃ loss rate of the SLMed 3D samples. During this study, although the Al₂O₃ loss rate of the single-track is only 33%, the loss rate of SLMed 3D samples increases significantly to 97% when the hatching space of 60 μm and scanning speed of 200 mm/s are utilized, i.e., almost no Al₂O₃ in the 3D sample. Thus, it is more important to reduce the remelting, i.e., overlap rate for reducing the element/phase loss. This study is a benefit for understanding and reducing the element/phase loss in SLM.     

20#钢激光熔覆-重熔Ni基涂层及其高温磨损行为

应用激光熔覆法,采用镍基NiCrSiB粉末,在20#钢表面制备了熔覆涂层,并用激光重熔涂层。观察了熔覆-重熔层的形貌,检测了其相组成和高温耐磨性能,结果表明:所制得熔覆-重熔层组织均一、致密,与基体形成了良好的冶金结合;经重熔处理后,熔覆层表面的裂纹显著减少;熔覆-重熔层的硬度提高到基体的5倍,高温磨损率约为基体的1/3。熔覆-重熔层耐磨能力的增强除因其与基体形成了良好的冶金结合和硼化物、硼碳化物等析出相的强化作用外,也是重熔减少微裂纹的结果。     

电渣重熔Mn18Cr18N钢铸态显微组织

通过电子探针和透射电镜的观察，发现电渣重熔Ｍｎ１８Ｃｒ１８Ｎ钢的铸态组织主要由奥氏体和大块碳化物组成，晶界上有少量的条状相。采用１２５０℃１２ｈ的扩散退火可以消除铸态组织的显微偏析而使成分均匀。     

200t大型电渣炉成分均匀性研究

为成分有差异的多支异炉号自耗电极电渣重堵100t以上大钢锭开发了成分均匀性控制工艺。试验和生产性试验表明，大型电渣锭的成分可达高度均匀性水平，使整支锭成分波动在C≤±0．01％，Si、Mn≤±0．015％，Cr、Mo≤±0．02％范围。此种以小拼大熔炼大电渣锭的工艺，其设备投资仅为传统方法的10％。     

高氮双相不锈钢6.2 t扁锭电渣重熔的工艺实践

2205双相不锈钢6.2 t 200 mm×1250 mm扁锭（/%:0.015~0.016C,0.15~0.16Si,1.35~1.39Mn,0,005~0.006S,0.023~0.024P,22:78~22.95Cr,5.40Ni,3.15~3.17Mo,0.193~0.194N）由20 t双极串联抽锭电渣重熔炉生产。通过采用50CaF₂-19Al₂O₃-19CaO-6MgO-6SiO₂液态熔渣,控制抽锭速度12 mm/min,电极熔化速度1100~1200 kg/h等工艺措施,扁锭表面质量良好,表面修磨量≤3 mm,满足轧制要求。     

金属半固态加工技术的研究进展

金属半固态加工技术是21世纪前沿性金属加工技术,具有高效、节能、近终型生产和成型件性能高等许多优点。本文从金属半固态浆料和坯料制备、半固态金属及合金坯料的二次加热以及半固态成型3个方面论述了半固态加工技术的现状,并指出了当前金属半固态加工技术的研究重点和发展前景。     

电渣重熔过程炉渣中氟化物挥发的研究

对电渣重熔过程4元渣系和5元渣系氟化物挥发相关研究进行归纳和总结,通过渣成分活度计算模型对氟化物挥发反应进行了热力学分析,给出了不同碱度炉渣的挥发物挥发程度排序。结果表明,碱度在3.74～0.84,氟化物的挥发能力次序为MgF₂>AlF₃>SiF₄>AlOF。1200℃以上时,含氟化物炉渣尤其中高氟炉渣存在明显的失重现象。对ANF-6渣(/%:30Al₂O₃、70CaF₂),1400℃时,100 g渣样中氟化物的挥发速率可达到0.68g/min,AlF₃、SiF₄挥发应作为失重的主要原因。